As a secondary battery that can charge and hold electricity therein, a lead-acid storage battery, a nickel-cadmium storage battery, a lithium-ion secondary battery and so on have been developed and practically used, and a high-performance lithium-ion secondary battery attracts attention recently. The lithium-ion secondary battery uses an organic solvent and is used in a variety of usages by optimizing a cathode active material, an anode active material, an organic solvent electrolyte solution and so on.
The secondary battery is configured such that battery cells of the secondary battery are stacked in multi layers and electrically connected in parallel to increase the electric capacity to be stored.
In the lithium-ion secondary battery disclosed in Patent Document 1, a structure is employed in which a sheet-shaped separator 7 is folded like an accordion and positive electrodes and negative electrodes are alternately inserted therein as illustrated in FIG. 22. At cathode plates 8 and anode plates 9, lead parts 8a, 9a projecting to sides opposite each other from a continuous body of the separator are provided, and the lead parts 8a, 9a of the cathode and anode are separately gathered together and electrically connected with one another.
The continuous body of the separator 7 is composed of a porous film formed with fine pores made of a synthetic resin such as a polyolefin-based resin. The cathode plate 8 is formed by applying a cathode active material such as lithium transition metal composite oxide on both surfaces of sheet-shaped metal foil. The anode plate 9 is formed by applying an anode active material such as carbon material on both surfaces of sheet-shaped metal foil. A plurality of the cathode plates and a plurality of the anode plates are separately gathered together so that the unit cells are connected in parallel.
Since the lithium-ion secondary battery uses a flammable organic solvent electrolyte solution, the organic solvent electrolyte solution decomposes by the electrode reaction and thereby expands the outer can of the battery to possibly cause leakage of the electrolyte solution in some cases, and therefore a polymer lithium-ion secondary battery has been developed for the purpose of reducing the size and weight and improving the safety. This is made by using a gelatinous electrolyte in place of the electrolyte solution used in the conventional lithium-ion secondary batteries. The gelatinous electrolyte contains the electrolyte solution and further contains a matrix polymer such as polyethylene oxide, polyvinylidene fluoride-propylene hexafluoride copolymer, polyacrylamide, polyacrylonitrile.
The lithium-ion secondary battery using the gelatinous electrolyte is disclosed, for example, in Patent-Document 2 in which a lithium-ion secondary battery 1 configured such that a unit cell is composed of a cathode plate 3 with a terminal tab 2 projecting from the end portion, a gelatinous electrolyte 4 formed in a film form, a separator S, and an anode plate 6 with a terminal tab 5 projecting from the end portion, and a plurality of unit cells are alternately stacked and subjected to heating press to form a multilayer membrane electrode assembly, is packed and sealed by a laminate film or the like such that a plurality of cathode plates and a plurality of anode plates are separately gathered together and the unit cells are connected in parallel as illustrated in FIG. 23.
Further, the structure disclosed in Patent-Document 3 as a stacked structure of an all-solid lithium-ion secondary battery has cathode layers having a cathode active material to/from which lithium ions move in/out, anode layers having an anode active material to/from which lithium ions move in/out, and solid electrolyte layers arranged between the cathode layers and the anode layers, in which two adjacent solid electrolyte layers are connected by an insulating layer, and two adjacent stacks are stacked such that the anode layers constituting the respective stacks 4 or the cathode layers constituting the respective stacks 4 are in contact with each other.
On a pair of side surfaces of the stacked stacks, a first current collector and a second current collector are arranged respectively. The first current collector is in contact with the cathode layer but not in contact with the anode layer so that the first current collector and the anode layer are separated by the insulating layer. Further, the second current collector is in contact with the anode layer but not in contact with the cathode layer so that the second current collector and the cathode layer are separated by the insulating layer. Terminal portions are arranged on the right and left ends and collector foil is arranged on the lower end, and a fastening load is applied thereto via the terminal portions. The stacked stacks are electrically connected with each other in parallel using the first current collector as the cathode and the second current collector as the anode.
As the stacked structure of the all-solid lithium-ion secondary battery, structures utilizing the fact that the solid electrolyte layer becomes the insulating film for paired electron conduction between adjacent cells are disclosed in Patent-Document 4 and Patent-Document 5.
In Patent-Document 4, the stack is an integrally sintered body, and a plurality of blocks in each of which battery cells of the secondary battery are stacked in series are joined together in parallel. In each of the serial blocks, a plurality of battery cell units, each having a cathode current collector layer, a cathode active material layer, an ion conductive inorganic material layer (solid electrolyte material layer), an anode active material layer and an anode current collector layer in this order, are joined together in series. The cathode current collector layers and the anode current collector layers other than those arranged at outermost layers are not extended out to end surfaces of the serial block, and the cathode current collector layer and the anode current collector layer located at the outermost layers extend out at least to different portions of the end surfaces of the serial block respectively, and all of the cathode current collector layers and all of the anode current collector layers located at outermost layers of the plurality of the serial blocks extend out at least to different portions of the end surfaces of the stack respectively.
A multilayer stacked battery in Patent-Document 5 is in a multilayer stacked structure composed of a plurality of battery cells at a plurality of stages, each of the battery cells being a thin film solid lithium-ion secondary battery composed of an anode active material layer and a cathode active material layer capable of absorbing and releasing lithium ions, a solid electrolyte layer arranged between them and having a function of electron-conductively separating and isolating them, and cathode side and anode side current collector layers composed of metal films having a function of collecting current directly above and directly below the active material layers. The multilayer stacked battery further utilizes the function of the solid electrolyte layer becoming an insulating film for paired electron conduction between adjacent cells, and utilizes the function of the current collector layer (metal film) becoming an insulating film for paired ion conduction between the active material layers of upper and lower adjacent cells, to coat and insulate the surroundings of the cathode and anode active material layers at the peripheral outside positions, by the solid electrolyte layer and the current collector layers. Further, the outer rim portions of the current collector layers are covered and insulated by the solid electrolyte layer at the outer rim portion outside positions. In the stacked structure, the structure in the plurality of stages is formed on one substrate by stacking the respective layers in order without using a new insulating film between the individual battery cells.
Further, Patent-Document 6 discloses an all solid-type battery structure in which it is easy to take out the electrode terminal of the all solid-type battery, and realize the electrical parallel connection of a plurality of batteries only by piling up battery cells of the secondary battery. The structure is made such that, as illustrated in FIG. 24, insulating substrates 106 each having a metal pattern 102 (taking-out electrode) and a contact hole 104 are arranged at the top and the bottom, and a power generating element 108, in which a cathode current collector, a cathode, a solid electrolyte, an anode, and an anode current collector are stacked, is arranged to be sandwiched between the insulating substrates 106. For example, one of the cathode and anode current collectors of the power generating element 108 is electrically connected to any of the metal patterns 102 of the insulating substrates 106 covering it via the contact hole 104, and the other current collector is electrically connected to any of the metal patterns 102 of the insulating substrates 106 covering it via the contact hole 104. The upper and lower insulating substrates 106 are bonded together to seal the power generating element, conduction is established by the metal patterns 102 via through holes 110 penetrating the insulating substrates 106 holding the power generating elements 108 sandwiched between them, from the metal pattern 102 connected via the contact hole 104 on the front surface of the sealed body to the metal pattern 102 not connected via the contact hole 104 on the rear surface.
The all solid-type battery structure, in which a cathode terminal and an anode terminal realized by taking-out electrodes exist on the upper surface of the unit cell, and a cathode terminal and an anode terminal also similarly exist on the lower surface, thereby enabling electrical parallel connection only by piling the unit cells.
Further, Patent-Document 7 discloses an electrode assembly capable of providing a battery in which modification of the shape and adjustment of the capacity are easy. In an ordered array of segments of the electrode assembly, segments extend while arranged side by side in one direction within one virtual plane. The number of virtual planes of the segments extending while arranged side by side is two or more, and the directions in which the segments extend within the virtual planes are different. The segments within one virtual plane may cross, having a difference of 90°, the segments within another plane. The interval between the segments is 0, or have an arbitrary size capable of providing molding workability of the battery, for example, 5 μm to several thousands μm. In some embodiments, between planes each composed of segments extending while arranged side by side, a separation film is further arranged.